1. Technical Field
The present invention relates to III-nitride crystal growth methods in which, onto a major surface of a first III-nitride crystal, a second III-nitride crystal is grown by hydride vapor-phase epitaxy (HVPE), under a high-temperature ambient exceeding 1100° C.
2. Description of the Related Art
III-nitride crystals such as GaN crystal are ideally suited to semiconductor-device applications including light-emitting devices and electronic devices. Large-scale III-nitride crystal is consequently in demand. Therein, vapor-phase growth—HVPE in particular—is a technique suited to growing large-scale III-nitride crystal efficiently, since the crystal-growth speeds are high.
Meanwhile, liquid-phase growth—in particular, solution methods in which a source-material melt is employed—is a technique suited to growing low-dislocation density, highly crystalline III-nitride crystal.
In this respect, in order to efficiently grow low-dislocation density, highly crystalline III-nitride crystal that is large-scale, B. Lucznik et al., “Deposition of Thick GaN Layers by HVPE on the [sic] Pressure Grown GaN Substrates,” Journal of Crystal Growth, Vol. 281, 2005, pp. 38-46, (Non-Patent Document 1), propose a method of growing GaN crystal by HVPE into a GaN crystal substrate obtained by a solution-growth technique. Non-Patent Document 1: “Deposition of Thick GaN Layers by HVPE on the [sic] Pressure Grown GaN Substrates,” Journal of Crystal Growth, Vol. 281, 2005, pp. 38-46.
Nevertheless, large-scale crystal is not obtainable with the method in foregoing Non-Patent Document 1. To be specific, the problem is that if GaN crystal is grown following the growth method in foregoing Non-Patent Document 1 at temperatures higher than 1100° C. onto a GaN crystal substrate obtained by solution growth, numerous regions where GaN crystal does not grow onto the major surface of the GaN crystal substrate (crystal non-growth regions) appear.
Therein, in order to investigate the cause of this sort of problem, the present inventors conducted several different analyses, utilizing a variety of methods, of the surface layers in the just-noted regions. As a result, the present inventors came to complete the present invention by discovering that under secondary ion mass spectrometry (SIMS) the concentration of alkali metal atoms in the regions is 1.0×1018 cm−3, and further by discovering that GaN crystal will grow onto a GaN crystal substrate in which the concentration of alkali metal atoms is less than 1.0×1018 cm−3.
Thus an object of the present invention, in order to resolve the problem discussed above, is to make available a method of growing, across the entirety of a major surface of a first III-nitride crystal (e.g., a GaN crystal substrate), a second III-nitride crystal (e.g., GaN crystal) by HVPE, in an ambient temperature higher than 1100° C.